Hair extension



FIG. 1 is a front view of a hair extension showing my new design;

FIG. 2 is an enlarged front view of a portion of the hair extension within the area identified by broken circle “FIG. 2” in FIG. 1.

FIG. 3 is a back view of thereof; and,

FIG. 4 is an enlarged back view of a portion of the hair extension within the area identified by broken circle “FIG. 4” in FIG. 3. 

CLAIM The ornamental design for a hair extension, as shown and described. 